A semiconductor device is known which has an integral package of a power semiconducting element and a regulatory IC for controlling the power semiconducting element. As shown in FIG. 8, the semiconductor device of this type comprises a support plate 3; a power semiconducting element 21 mounted on support plate 3; a layered structure of a regulatory IC 22 mounted on power semiconducting element 21 or, as shown in FIG. 9, an apposed structure of a regulatory IC 22 secured on support plate 3 away from power semiconducting element 21. For example, FIG. 4 of Japanese Patent No. 2,566,207 discloses a semiconductor device of such a layered structure.
Such a semiconductor device naturally requires the semiconducting structure of good thermally radiative property because power semiconducting element 21 eradiates a larger amount of heat than regulatory IC 22 does. However, semiconductor device shown in FIG. 8 cannot indicate good thermally radiative property due to the less heat discharging performance because heat emitted from power semiconducting element 21 is discharged to outside only through support plate 3. In some cases, it would be preferable to thermally isolate regulatory IC 22 from power semiconducting element 21, especially in view of the function of semiconductor device which involves heating power semiconducting element 21 and power-saving regulatory IC 22. In this case, there would be a risk of disadvantageously deteriorating the electric property of regulatory IC 22 which may be overheated by heat directly transferred to regulatory IC 22 from power semiconducting element 21.
On the other hand, in semiconductor device of the apposed structure shown in FIG. 9 wherein power semiconducting element 21 and regulatory IC 22 are juxtaposed on support plate 3, it is possible to prevent direct heat transmission from power semiconducting element 21 to regulatory IC 22, however, it is still defective due to the inferior heat radiation since heat is inadequately discharged from power semiconducting element 21 to outside only through support plate 3. The apposed structure of FIG. 9 also has an additional disadvantage because it requires larger plane size of semiconductor device in the apposed structure of power semiconducting element 21 and regulatory IC 22 on support plate 3.
An object of the present invention is to provide a semiconductor device which has semiconducting elements stacked in the layered structure with an excellent thermally radiative property.